HTC's top-of-the-line Android smartphone, HTC Sensation, is now available in Australia through Telstra -- providing yet another potentially confusing option for business travellers in the market for a new smartphone.

So how does the Sensation differ from HTC's popular Desire HD (sold exclusively in Australia through Vodafone) and the iPhone 4?

For a start, the Sensation supports "HD Voice", which allows higher sound quality phone calls. It's only supported on the Telstra network at the moment.

Telstra claims that HD Voice is better at cancelling out background noise in busy environments, although the person you're calling also needs to have a HD Voice compatible handset. Other phones that support HD Voice include Nokia 6720, E52, E72, N8, HTC Desire S and Sony Ericsson Neo-Xperia.

Physical comparisons

The Sensation is 20 grams lighter than the Desire HD, and half a millimetre thinner.

Compared to the iPhone 4, it's 11 grams heavier, and 2mm thicker. The iPhone 4 is about a centimetre shorter.

A key feature of the Sensation is that its 4.3" screen is one of the highest resolution on any smartphone, packing 540x960 pixels, compared to Desire HD's 480x800.

That's still not quite as high as the iPhone 4's 640x960px, but it's very close -- and of course the iPhone's display is smaller at 3.5".

Surprisingly, the Sensation has a little bit less inbuilt storage than the Desire HD - 1GB compared to 1.5GB. Both handsets come with 8GB card in the box, and you can buy a micro-SD card up to 32GB to beef up the storage if you need it. The iPhone 4 comes with a minimum of 16GB, and is available up to 32GB.

Software improvements

One of the most noticeable improvements with the Sensation is HTC's Sense 3.0 user interface. It is the first phone in Australia to have the new software, which sits on top of Google Android, providing a much slicker look and feel than Android provides by itself. The Desire HD had the more limited Sense 2.0.

One of the big enhancements in Sense 3.0 is the "active lock screen" where you can get updates from the phone without unlocking it. These updates include an interactive photo album, friend stream, weather, stocks and clock.

You can also take photos in lock mode -- a feature that HTC has beaten Apple to the punch with, though it's coming in iOS 5, which is due for release in coming months.

Speed and interface responsiveness is really where the Sensation wins over the Desire HD (which itself was a very fast phone). It has a 1.2GHz, dual-core processor -- two processors in one -- where the Desire HD only had a single core, 1GHz chip. The iPhone 4 uses a single core chip, though Apple's iOS software feels very fast on it.

The Sensation also uses the very latest version of Google Android -- 2.3 "Gingerbread" -- whereas Desire HD still only uses version 2.2, "Froyo". The difference between the two is that running numerous apps at once and switching between them is much snappier under Android 2.3.

A snappier camera

The camera in the Sensation is the same 8 megapixel one used in the Desire HD, but HTC has improved the software that runs it, adding digital image stabilisation, touch-to-focus and instant capture (which, as the name suggests, snaps a photo at the split-second you press the camera button.)

The iPhone 4 uses a 5 megapixel camera, which takes outstanding photos and video, but can take a long time to start up.

The Sensation's camera can also shoot full HD 1080P video, which is pretty amazing for a smartphone.

What it costs

You can get it for $0 by signing on to a 24 month $79 Telstra cap plan.

Any plan lower than that and you'll be paying $30 a month for the handset on top of the plan fee, which practically makes the $79 plan the only logical option.

If you don't want a contract, it's $796 upfront through Telstra shops.

The plan mentioned above includes $800 worth of calls, unlimited SMS within Australia, unlimited voicemail and 2GB of data.